1. Field of the Invention
This invention relates to an inkjet printing apparatus with a plurality of inkjet heads.
2. Description of the Related Art
A conventional inkjet printing apparatus having an inkjet head with many inkjet nozzles performs cleaning to the inkjet head by suction (suction purge) so as to eliminate printing failure, so-called nozzle clogging, resulting from partial clogging of the inkjet nozzles.
For instance, Japanese Patent Publication No. 2008-213216 discloses an inkjet recorder. The inkjet recorder includes caps covering ejection port groups (an inkjet head) individually, and a pump supplying ink from the ejection ports (inkjet nozzles) into the caps. The inkjet recorder further includes a connection channel connecting the caps to the pumps, respectively, and on/off valves provided on the channel individually. In the inkjet recorder, the on/off valves on the connection channel in communication with each of the caps of the group of ejection ports (inkjet heads) are selectively opened, whereby suction purge can be achieved in which only a cap covering the inkjet nozzle with no ink being ejected therefrom is connected to the pump to be sucked individually.
Another inkjet printing apparatus has also been proposed. The inkjet printing apparatus includes a cleaning mechanism that allows overall suction for sucking collectively a plurality of inkjet heads and individual suction for sucking every inkjet head individually. See International Publication WO2007/058139. The cleaning mechanism includes an individual suction cap that connects one cap, selected from caps covering a plurality of inkjet heads, to a pump via a tube; the caps connected to the pump via a tube branched to the caps; a first on/off valve switching suction of the plurality of caps simultaneously; and a second on/off valve switching suction of only the individual suction cap. Overall suction is performed while the plurality of inkjet heads are all covered with the caps to open the first and second on/off valves. Individual suction is performed while only one inkjet head is covered with the individual suction cap to close the first on/off valve and to open the second on/off valve. This allows individual suction for the inkjet head to be sucked.
The apparatus disclosed in Japanese Patent Publication No. 2008-213216 has a drawback as under. That is, many electromagnetic on/off valves corresponding to the number of caps have to be disposed, resulting in an enlarged apparatus and increased production costs. The apparatus has another drawback as under. That is, many electromagnetic on/off valves are driven, resulting in increased power consumption and running costs.
Moreover, the apparatus of WO2007/058139 performs cleaning to every inkjet unit having a plurality of inkjet heads being arranged in one direction. Consequently, when individual suction is performed to the inkjet heads, it takes longer time to move the inkjet unit to align the inkjet heads with the individual suction cap depending on arrangement of the inkjet heads to be sucked in the inkjet unit. This causes a drawback that longer time is required for cleaning the inkjet heads.
In order to solve the above-mentioned drawbacks, one object of this invention is to provide an inkjet printing apparatus with a simple construction that allows reduction in ink consumption and rapid cleaning of inkjet heads.